The present invention relates to a cooling element designed particularly for furnaces. The invention also relates to a method for manufacturing cooling elements.
In connection with industrial furnaces, such as flash smelting furnaces, blast furnaces and electric furnaces, there are used massive cooling elements that are typically made of copper. They are used in extreme working conditions, where copper is subjected to intensive corrosion strains caused by the furnace atmosphere and even by contacts with the molten material. For example, in an SO2 atmosphere, copper corrosion is caused, among others, by oxidizing and sulphatizing reactions, which in the worst case can result in material losses of even tens of millimeters on the corroded surfaces.
The object of the invention is to realize a cooling element whereby the problems known in the prior art can be avoided. Thus the object of the invention also is to achieve a cooling element that has a longer working life than the ones known in the prior art. Another object of the invention is to realize a method for manufacturing a cooling element that is more resistant than the ones known in the prior art.
The invention is based on an idea according to which on the surface of a cooled element consisting mainly of copper there is attached, by means of a diffusion joint, a steel surface that has a better corrosion resistance.
The invention is characterized by what is specified in the appended claims.
The invention has several remarkable advantages. The method of applying a surface layer by means of a diffusion joint enables an excellent heat transfer over the junction. The suggested joining method allows the surface layer to be joined to the cooling element housing at temperatures that are even hundreds of degrees lower than the melting point of copper. The cooling element according to the invention has a remarkably better corrosion resistance than the cooling elements of the prior art. Consequently their working life before replacement is remarkably longer than in the prior art.
In this application, the term copper refers to, apart from objects made of copper, also to alloy materials with a copper content that essentially includes at least 50% copper. The term stainless steel in this application refers mainly to austenitic alloy steels, such as stainless and acid-proof steels.